#include<stdio.h>
  int main()
  {
      char i;
      printf("please input a letter,or 0 to stop.\n");
      scanf("%c",&i);
	  //i = getchar();
	  //printf("%c\n",i);
      while(i!='0')
      {
          if(i>64&&i<91)
          {
              printf("%c\n",i);
          }
          else if(i>96&&i<123)
          {
              printf("%c\n",i-32);
          }
		  else if(i == '\n');
          else
          {
              printf("error input,please input again\n char=%c\n",i);
          }
          scanf("%c",&i);
		 //i=getchar();
      }
      return 0;
  }
